This invention relates to a screw driver for holding and tightening the screws on scissors, shears and other thin objects where great pressure must be exerted to tighten or to loosen the screw.
Whenever it is necessary to tighten or loosen the screw on scissors, shears or the like it is necessary to apply substantial pressure to the screw and it is very important that the screw driver blades engage the kerf or the driving slot on the screw squarely. Since the thickness of the scissors or shears vary, the point of the screw driver blade engages the screw also varies, and the screw driver blade will not squarely engage the driving slot in the screw unless the length of the screw driver blade is adjusted so that it will engage the driving slot in the screw when the two jaws are parallel.
In the past, attempts have been made to provide pressure gripping screw drivers for scissors. One example is found in U.S. Pat. No. 1,795,054. The device in this patent is a pliers-like device with two jaws for clamping the scissors and the screw. One of the jaws has, extending therethrough, a screw driver for engaging the driving slot in a screw on scissors or the like. However, this tool will only properly engage one thickness of shears or scissors. If a shears or scissors of different thickness is tightened or attempted to be tightened by the tool in this patent proper engagement of the screw driver bit 4 with the driving slot or kerf of the screw will not be made and as a result the driving slot in the screw may be mangled or ruined. This patent also provides a ratcheting drive for the screw driver.
Another pressure screw driver device is found in U.S. Pat. No. 2,352,917. The tool in this patent has two screw driving mechanisms. One is for very thin scissors and the other for enlarged heavy duty shears. However, this device is still limited to properly engaging only two sizes of shears or scissors and cannot be adjusted to properly engage the screws on a variety of thicknesses of shears or scissors.
Another tool is found in the combined pliers and screw driver of U.S. Pat. No. 2,079,863. The combined pliers and screw driver shown in this patent includes a rachet or spring-loaded engaging drive between the clamping jaws and the screw driver blade, for driving the screw driver in either direction. However, this device will only properly fit scissors of a predetermined thickness and a different tool must be used for scissors or shears having a greater or lesser thickness than what the tool is designed for.
Other tools for this purpose are shown in U.S. Pat. Nos. 1,191,873, 1,802,666, and 2,005,723, but none of these patents disclose or teach a tool which is adapted to fit shears or scissors of a multiplicity of thickness or sizes.